The US Justice Department must decide by August 5 whether it will seek to block a tie-up between Alaska Air Group Inc. and Hawaiian Holdings Inc., the airlines said in securities filings.

The airlines said they had turned over all documents requested by antitrust enforcers, triggering a 90-day deadline for a decision that will expire on August 5.

The agency opened an in-depth review of the transaction in February. The Biden administration has taken a tough stance on airline mergers suing to break up a partnership between American Airlines Group Inc. and JetBlue Airways Corp., and to block JetBlue’s proposed deal to buy Spirit Airlines Inc.

Alaska’s proposal values Hawaiian’s equity at about $1 billion, and includes about $900 million of debt. Alaska will be the parent holding company, headquartered in Seattle, with Alaska Airlines and Hawaiian Airlines continuing to operate under their separate brands.